Bio-Luminescence

As with many other deep-sea species, O. deletron can display areas of bio-luminescence when threatened. The bio-luminescence is controlled by chromatophore layers surrounding the photogenic tissue on each of the eight arm tips of the squid. In a study performed by Bush et al. in 2009, observations were made about this characteristic trait during two dives of remotely operated vehicles controlled by the Monterey Bay Aquarium Research Institute. Bush and her colleagues collected video footage from these dives in order to further observe this bio-luminescent behavior.

From this footage, they discovered three main ways in which bio-luminescence was expressed in the squid. O. deletron could display an intermittent bio-luminescence, where the eight photophores were not synchronized and could flash at different rates. Also observed was a continuous bio-luminescence of more than one minute and brief, simultaneous bio-luminescence of the eight arm tip photophores.

From these observations and various methods of expression, they came to the conclusion that the bio-luminescence was used as a warning for predators and a possible escape tool. When an individual squid has become aware of a possible predator, it can use its arm-tip photophores as a conspicuous way to communicate to the predator that the squid knows they are there. This can lead to the avoidance of an attack from the predator. If this behavior does not work, though, the squid may illuminate all eight of the photophores on their arm tips simultaneously, briefly blinding the predator and, hopefully, allowing for their escape.

Figure 1. Different stages of arm-tip photophore bioluminescence in Octopoteuthis deletron. (A) Chromatophores contracted. (B) Chromatophores partially expanded. (C) Chromatophores fully expanded.

Figure 2. Control of arm-tip photophores through the use of chromatophore screening in O. deletron. The arrows follow one arm tip from nearly completely covered photophore to a nearly fully exposed luminescing photophore. Figures are from individual video frames taken in situ at 645 m depth by an MBARI ROV.